A recent review conducted by Australian researchers has raised questions about the potential link between cat ownership and an increased risk of schizophrenia-related disorders.
The study, which analyzed 17 research papers spanning over four decades and involving 11 countries, including the US and the UK, highlights the need for further investigation into this intriguing association.
The peer-reviewed study, published in Schizophrenia Bulletin, led by psychiatrist John McGrath and researchers from the Queensland Centre for Mental Health Research, revisited the hypothesis initially proposed in a 1995 study that owning a cat could be linked to a higher risk of schizophrenia.
The proposed connection hinges on exposure to Toxoplasma gondii, a parasite that can be transmitted through undercooked meat, contaminated water, cat bites, or contact with infected cat feces.
T. gondii, generally considered harmless, has been the subject of extensive research due to its potential to infiltrate the central nervous system and influence neurotransmitters.
Links between parasite, personality changes
Past studies have suggested links between the parasite and personality changes, the emergence of psychotic symptoms, and various neurological disorders, including schizophrenia.
However, establishing a definitive causal relationship between T. gondii and these changes, or proving that the parasite is transmitted from cats to humans, remains challenging.
The new analysis of 17 studies found a “significant positive association between broadly defined cat ownership and an increased risk of schizophrenia-related disorders.”
After adjusting for various factors, the researchers determined that individuals exposed to cats had approximately twice the odds of developing schizophrenia.
It’s important to note that 15 of the 17 studies examined in the analysis were case-control studies, which cannot establish a cause-and-effect relationship and may not adequately account for confounding factors. Additionally, some of the studies reviewed were of low quality, which the authors acknowledge.
The findings also displayed inconsistencies across studies, with some suggesting associations in unadjusted models that might have been influenced by other factors.
For example, one study found no significant link between owning a cat before age 13 and later developing schizophrenia but did find connections when narrowing cat ownership to a specific period (Ages 9 to 12). This inconsistency raises questions about the critical time frame for cat exposure.
Another study involving psychology students in the US found no connection between owning a cat and schizotypy scores but did reveal that those who had experienced a cat bite had higher scores compared to those who had not.
Meanwhile, a study encompassing individuals with and without mental disorders identified a connection between cat bites and higher scores on tests measuring specific psychological experiences, but it suggested that other pathogens, such as Pasteurella multocida, might be responsible.
The review provides support for an association between cat ownership and schizophrenia-related disorders, but it underscores the need for more high-quality research based on large, representative samples to better understand the role of cat ownership as a potential risk factor for mental disorders.